Question on Installing Stainless Steel Brake Lines

How does keeping the brake pedal depressed stop fluid from being lost? I don't know much about braking systems but I would have thought it'd cause the fluid to be under pressure and would lose more fluid when removing the lines?
Genuinely interested to find out the answer/reason!

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This post was auto-generated based upon a question asked on our tech article page here:

[Nick at Pelican Parts]

The pistons in the master blocks fluid from the reservoir from reaching the lines when depressed.

- Nick